U.S. patent number 5,492,861 [Application Number 08/112,711] was granted by the patent office on 1996-02-20 for process for applying structured layers using laser transfer.
This patent grant is currently assigned to Deutsche Forschungsanstalt fuer Luft-und Raumfahrt e.V.. Invention is credited to Hans Opower.
United States Patent |
5,492,861 |
Opower |
February 20, 1996 |
Process for applying structured layers using laser transfer
Abstract
In order to provide a process for applying structured layers of
a functional structure of a semiconductor component, with which
structured layers of a functional structure of a semiconductor
component can be produced as simply as possible and with as little
susceptibility as possible with respect to the quality of the
semiconductor components, it is suggested that a material film be
arranged above a surface region of a process substrate to be
provided with the structured layer, that the material film be acted
upon on its side remote from the process substrate by a focus of a
laser beam located in a defined position corresponding to the
structured layer to be produced and that with the laser beam in the
region of the focus the material from the material film migrate to
the surface region.
Inventors: |
Opower; Hans (Krailling,
DE) |
Assignee: |
Deutsche Forschungsanstalt fuer
Luft-und Raumfahrt e.V. (Bonn, DE)
|
Family
ID: |
25918192 |
Appl.
No.: |
08/112,711 |
Filed: |
August 26, 1993 |
Foreign Application Priority Data
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Sep 3, 1992 [DE] |
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42 29 398.7 |
Sep 26, 1992 [DE] |
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42 32 373.8 |
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Current U.S.
Class: |
438/478;
148/DIG.93; 257/E21.159; 427/597; 438/676; 438/940 |
Current CPC
Class: |
C23C
14/048 (20130101); C23C 14/28 (20130101); G03F
7/16 (20130101); H01L 21/2855 (20130101); Y10S
148/093 (20130101); Y10S 438/94 (20130101) |
Current International
Class: |
G03F
7/16 (20060101); H01L 21/02 (20060101); H01L
21/283 (20060101); H01L 021/268 (); C23C
014/14 () |
Field of
Search: |
;427/597,561 ;437/173
;148/DIG.90,DIG.93
;204/192.1,192.12,192.11,298.02,298.01,298.04 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
0002738 |
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Jul 1979 |
|
EP |
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2113336 |
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Sep 1971 |
|
DE |
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2523982 |
|
May 1975 |
|
DE |
|
1118429 |
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Oct 1984 |
|
SU |
|
Other References
W Marine, et al., Laser Ablation of Electronic Materials p. 89,
Elsevier Publishing-EMRS Monographs vol. 4, 1992. .
R. J. von Gutfeld, et al., Appl. Phys. Lett., 35(9) 1979 "Laser
Enhanced Electroplating and Maskless . . . ". .
R. T. Hodgson, et al., IBM Tech. Discl. Bulletin, vol. 21, #10,
1979, "Ohmic Contacts Made by Lasers". .
J. P. Coullahan et al., IBM, Tech. Discl. Bulletin, vol. 22, #6,
1979 "Chip Passivation Technique". .
J. Bohandy, et al., "Metal deposition at 532 nm using a laser
technique," J. Appl. Phys. vol. 63(4), Feb. 15, 1988, pp.
1158-1162. .
J. Bohandy, et al., "Metal deposition from a supported metal film
using an excimer laser," J. Appl. Phys. vol. 60(4), Aug. 15, 1986,
pp. 1538-1539. .
F. J. Adrian, et al., "A study of the mechanism of metal deposition
by the laser-induced forward transfer process" J. Vac. Sci.
Technol. B, vol. 5, No. 5, Sep./Oct 1987, pp. 1490-1494. .
V. Schultze et al., "Laser-induced forward transfer of aluminum,"
Applied Surface Science vol. 52 (1991), pp. 303-309. .
R. J. Baseman, et al., "Laser induced forward transfer," Symp. Mat.
Res. Soc. 1988, pp. 237-242 Laser and Particle Beam, Chemical
Processing for Microelectronics. .
P. Matossi, Lehrbuch der Experimentalphysik, "Band III,
Optik,"Walter de Gruyter & Co., Berlin 1966, pp. 108-113. .
E. Fogarassy, et al., "Laser-induced forward transfer of
high-T.sub.c YBsaCuO and BiSrCaCuO superconducting thin films,"
Journal of Applied Physics vol. 66(1), Jul. 1, 1989, pp.
457-459..
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Primary Examiner: Hearn; Brian E.
Assistant Examiner: Radomsky; Leon
Attorney, Agent or Firm: Lipsitz; Barry R.
Claims
What is claimed is:
1. A process for applying structured layers of a functional
structure of a semiconductor component, comprising the steps
of:
arranging a material film above a surface region of a process
substrate to be provided with the structured layer;
acting upon the material film on its side remote from the process
substrate by a focus of a laser beam located in a defined position
corresponding to the structured layer to be produced;
heating the material in the material film with the laser beam in
the region of the focus so that material from the material film
migrates from the focus region to the surface region; and
producing the structured layer by overlapping application of
material from the focus region of the material film to the process
substrate.
2. A process as defined in claim 1, wherein the material film is
arranged on a carrier permeable to the laser beam.
3. A process as defined in claim 2, wherein said carrier is a rigid
element.
4. A process as defined in claim 2, wherein said laser beam
generates a plasma that penetrates a thickness of the material
film.
5. A process as defined in claim 4, wherein the plasma is generated
in a film plane with an expansion corresponding approximately to a
shape of the laser beam as it converges toward said focus.
6. A process as defined in claim 1, wherein the material film is
arranged on a transparent carrier permeable to the laser beam and
an optical focusing means for the laser beam is arranged on a side
of the transparent carrier remote from the material film.
7. A process as defined in claim 6, wherein prior to an application
of material from the material film to the process substrate, the
material film itself is applied to the carrier by means of the
laser used for applying the structured layer.
8. A process as defined in claim 7, wherein the laser beam
irradiates the carrier for applying the material thereto.
9. A process as defined in claim 7, wherein the carrier is arranged
at a distance from a surface of a material target for applying the
material film.
10. A process as defined in claim 9, wherein said distance is in a
range of from about 1 to 5 millimeters.
11. A process as defined in claim 9, wherein the material of the
material target is heated on its surface, expands in the direction
of the carrier and is deposited on the carrier.
12. A process as defined in claim 9, wherein the laser beam is
focused onto a surface of the material target.
13. A process as defined in claim 6, wherein the focus of the laser
beam is moved relative to the carrier for the structured
application of the material from the material film onto the
substrate.
14. A process as defined in claim 13, wherein the focus is moved by
movement of the laser beam relative to the carrier and to the
optical focusing means.
15. A process as defined in claim 1, wherein the focus is selected
in the film plane such that its diameter is less than a dimension
of the structured layer to be applied in a plane parallel to the
film plane.
16. A process as defined in claim 1, wherein the laser beam
consists of a plurality of laser pulses following one another in a
timed sequence.
17. A process as defined in claim 16, wherein with each laser
pulse, a transfer of material occurs from a focus region of the
material film onto the process substrate.
18. A process as defined in claim 16, wherein the focus regions of
successive laser pulses are positioned on the material film so as
not to overlap.
19. A process as defined in claim 16, wherein the focus regions of
successive laser pulses are positioned on the material film so as
to be adjacent one another.
20. A process as defined in claim 16, wherein the focus from laser
pulse to laser pulse is moved relative to the material film.
21. A process as defined in claim 1, wherein the material film is
moved relative to the process substrate.
22. A process as defined in claim 1, wherein the material film is
arranged at a distance from the surface region of the process
substrate, said distance being less than ten times a diameter of
the focus.
23. A process as defined in claim 1, wherein the material film has
a material composition functionally ready for the structured layer
of the functional structure.
24. A process as defined in claim 1, wherein the application of the
structured layer is performed under high vacuum or ultra-high
vacuum.
25. A process for applying structured layers of a functional
structure of a semiconductor component, comprising the steps
of:
arranging a material film above a surface region of a process
substrate to be provided with the structured layer;
generating a laser pulse having a duration of between about 1 and
100 picoseconds, a focus of said laser pulse, located in a defined
position corresponding to the structured layer to be produced,
acting upon the material film on its side remote from the process
substrate; and
heating the material in the material film with the laser pulse in
the region of the focus with a light density greater than 10.sup.8
w/cm.sup.2 so that material from the material film migrates from
the focus region to the surface region;
wherein the structured layer is produced on the process substrate
by overlapping application of material from the focus region of the
material film.
26. A process as defined in claim 25, wherein the focus is selected
in the film plane such that its diameter is less than a dimension
of the structured layer to be applied in a plane parallel to the
film plane.
27. A process as defined in claim 25, wherein the structured layer
is produced by multiple applications of structured part layers.
28. A process as defined in claim 25, wherein each structured part
layer is produced by a side-by-side application of material from
the focus regions.
29. A process as defined in claim 25, wherein the laser beam
consists of a plurality of laser pulses following one another in a
timed sequence.
30. A process as defined in claim 29, wherein with each laser
pulse, a transfer of material occurs from a focus region of the
material film onto the process substrate.
31. A process as defined in claim 29, wherein the focus regions of
successive laser pulses are positioned on the material film so as
to be adjacent one another.
32. A process as defined in claim 29, wherein the focus from laser
pulse to laser pulse is moved relative to the material film.
33. A process as defined in claim 25, wherein the material film is
moved relative to the process substrate.
34. A process as defined in claim 25, wherein the material film is
arranged at a distance from the surface region of the process
substrate, said distance being less than ten times a diameter of
the focus.
35. A process as defined in claim 25, wherein the material film has
a material composition functionally ready for the structured layer
of the functional structure.
36. A process as defined in claim 25, wherein the application of
the structured layer is performed under high vacuum or ultra-high
vacuum.
37. A process as defined in claim 25, wherein the material film is
arranged on a carrier permeable to the laser beam.
38. A process for applying structured layers of a functional
structure of a semiconductor component, comprising the steps
of:
arranging a material film above a surface region of a process
substrate to be provided with the structured layer;
generating a laser pulse having a duration of between about 1 and
100 picoseconds, a focus of said laser pulse, located in a defined
position corresponding to the structured layer to be produced,
acting upon the material film on its side remote from the process
substrate; and
heating the material in the material film with the laser pulse in
the region of the focus with a light density greater than 10.sup.8
w/cm.sup.2 so that material from the material film migrates from
the focus region to the surface region;
wherein the laser beam consists of a plurality of laser pulses
following one another in a timed sequence and the focus regions of
successive laser pulses are positioned on the material film so as
not to overlap.
39. A process for applying structured layers of a functional
structure of a semiconductor component, comprising the steps
of:
arranging a material film above a surface region of a process
substrate to be provided with the structured layer;
generating a laser pulse having a duration of between about 1 and
100 picoseconds, a focus of said laser pulse, located in a defined
position corresponding to the structured layer to be produced,
acting upon the material film on its side remote from the process
substrate; and
heating the material in the material film with with the laser pulse
in the region of the focus with a light density greater than
10.sup.8 w/cm.sup.2 so that material from the material film
migrates from the focus region to the surface region;
wherein the material film is arranged on a transparent carrier
permeable to the laser beam, an optical focusing means for the
laser beam is arranged on a side of the transparent carrier remote
from the material film, and the optical focusing means is coupled
to the transparent carrier by means of an immersion fluid.
40. A process for applying structured layers of a functional
structure of a semiconductor component, comprising the steps
of:
arranging a material film above a surface region of a process
substrate to be provided with the structured layer;
generating a laser pulse having a duration of between about 1 and
100 picoseconds, a focus of said laser pulse, located in a defined
position corresponding to the structured layer to be produced,
acting upon the material film on its side remote from the process
substrate; and
heating the material in the material film with the laser pulse in
the region of the focus with a light density greater than 10.sup.8
w/cm.sup.2 so that material from the material film migrates from
the focus region to the surface region;
wherein the material film is arranged on a transparent carrier
permeable to the laser beam, an optical focusing means for the
laser beam is arranged on a side of the transparent carrier remote
from the material film, and the optical focusing means is arranged
to focus the laser pulse on the carrier in a reflection-free
manner.
41. A process as defined in claim 40, wherein the optical focusing
means is integrally connected to the carrier.
42. A process for applying structured layers of a functional
structure of a semiconductor component, comprising the steps
of:
arranging a material film above a surface region of a process
substrate to be provided with the structured layer;
acting upon the material film on its side remote from the process
substrate by a focus of a laser beam, said laser beam consisting of
a plurality of successive laser pulses following one another in
timed sequence;
locating the focus regions of said successive laser pulses on the
material film so as not to overlap; and
heating the material in the material film with the laser beam in
the focus regions so that material from the material film migrates
from the focus regions to the surface region.
43. A process for applying structured layers of a functional
structure of a semiconductor component, comprising the steps
of:
arranging a material film on a carrier transparent to the laser
beam and above a surface region of a process substrate to be
provided with the structured layer;
arranging an optical focusing means for a laser beam on a side of
the transparent carrier remote from the material film, said optical
focusing means and said transparent carrier being coupled by means
of an immersion fluid;
acting upon the material film on its side remote from the process
substrate by a focus of said laser beam located in a defined
position corresponding to the structured layer to be produced;
and
heating the material in the material film with the laser beam in
the region of the focus so that material from the material film
migrates from the focus region to the surface region.
44. A process for applying structured layers of a functional
structure of a semiconductor component, comprising the steps
of:
arranging a material film on a carrier transparent to the laser
beam and above a surface region of a process substrate to be
provided with the structured layer;
arranging an optical focusing means for a laser beam on a side of
the transparent carrier remote from the material film, said optical
focusing means being arranged to focus the laser beam on the
carrier in a reflection-free manner;
acting upon the material film on its side remote from the process
substrate by a focus of said laser beam located in a defined
position corresponding to the structured layer to be produced;
and
heating the material in the material film with the laser beam in
the region of the focus so that material from the material film
thereby migrates from the focus region to the surface region.
Description
The invention relates to a process for applying structured layers
of a functional structure of a semiconductor component.
In accordance with the customary technology of today, a plurality
of process steps are performed for the production of semiconductor
components. These steps are carried out partially under vacuum
conditions and partially under normal atmospheric pressure and
chemical substances and foreign materials are used in them.
For example, structured layers are produced by multiple structuring
and doping of layers using photolithography, whereby the
photolithography comprises application of a photoresist layer,
exposure, development and etching of a substrate.
Furthermore, metallizations of a substrate are produced, for
example, by chemical deposition of metal layers.
The known technology is extremely susceptible with respect to the
resulting quality of semiconductor components since the substrate
comes into contact with a plurality of foreign substances. This
means that the possibilities of soiling are numerous and, in the
end, these impair the quality of the semiconductor components.
The object underlying the invention is therefore to provide a
process for applying structured layers of a semiconductor
component, with which structured layers of a functional structure
of a semiconductor component can be produced as simply as possible
and with as little susceptibility as possible with respect to the
quality of the semiconductor components.
This object is accomplished in accordance with the invention, in a
process of the type described at the outset, in that a material
film is arranged above a surface region of a process substrate to
be provided with the structured layer, that the material film is
acted upon on its side remote from the process substrate by a focus
of a laser beam located in a defined position corresponding to the
structured layer to be produced and that the material in the
material film is heated with the laser beam in the region of the
focus and material from the material film thereby migrates from the
focus region to the surface region.
The advantage of the inventive process is to be seen in the fact
that with this process it is possible to apply material from the
material film to exactly defined locations of the surface region of
the process substrate, whereby the individual locations can be
predetermined in a simple manner by the defined positioning of the
focus.
The material film can be made available in the most varied of
manners. For example, in a particularly advantageous embodiment the
material film is formed by a self-supporting foil, the material of
which is then applied to the surface region of the process
substrate.
In this case, it is particularly advantageous for a plasma to be
generated on the rear side of the foil by means of the laser beam,
this plasma accelerating foil material on the front side of the
foil onto the process substrate. While the plasma is being
generated, in particular, a pressure surge is generated in the foil
which acts through the entire foil and on the front side of the
foil leads to the acceleration of the foil material in the
direction towards the process substrate.
Alternatively to the provision of the material film in the form of
the self-supporting foil, in an additional advantageous embodiment
of the inventive solution the material film is arranged on a
carrier permeable to the laser beam. This embodiment offers the
great advantage that the material film itself no longer needs to
have any inherent stability, as with the foil, but that the
inherent or natural stability with respect to the exact positioning
can be achieved due to the carrier permeable to the laser beam and
so the material film can be selected to be considerably
thinner.
The carrier can, for example, be a transparent foil, on which the
material film is arranged. It is, however, even more advantageous
for the carrier to be a transparent element rigid in its form since
this element is easier to position and to move, and with it the
material film, due to its inherent form rigidity.
In the case where a material film arranged on a carrier is used, a
particularly preferred embodiment of the inventive solution
provides for a plasma penetrating a thickness of the material film
to be generated with the laser beam. This means that a different
process is selected for the acceleration of particles from the
material film in the direction towards the process substrate. In
this process, the plasma expands out of the focus region in the
direction of the process substrate, preferably in a cone at right
angles to a surface of the material film facing the process
substrate. Material from the material film is, therefore,
preferably applied in a region of the process substrate located
opposite the focus region.
In this embodiment, the material film preferably has a thickness of
less than 100 nm. In this respect, a thickness of approximately 5
to approximately 30 nm is particularly advantageous.
The laser power is, in this respect, preferably selected such that
the plasma is generated in a film plane having an expansion
corresponding approximately to the focus.
The focus is preferably selected in the film plane such that its
diameter is less than a dimension of the structured layer to be
applied in a plane parallel to the film plane. This has the great
advantage that the structured layer can be produced with a very
high degree of precision since its dimensions are produced by
multiple, side-by-side application of material from the focus
region to the process substrate.
Moreover, it is advantageous for the structured layer to be
produced by superposed application of material from the focus
region of the material film to the process substrate. This offers
the possibility of applying considerably thicker layers to the
process substrate despite the very thin material film.
No details have so far been given with respect to the laser used.
It is, for example, particularly advantageous for the laser beam to
be composed of a plurality of laser pulses following one another in
timed sequence. These laser pulses preferably follow one another at
a repetition rate in the region of approximately 10 kHz.
A mode of operation for the process has proven to be particularly
expedient, in which with each laser pulse a transfer of a focus
region of the material film onto the process substrate is carried
out so that a renewed positioning of the focus takes place on the
material film from laser pulse to laser pulse.
In this respect, it is particularly favourable, with regard to a
layer application which is as effective as possible, for the focus
regions of successive laser pulses to be positioned on the material
film so as not to overlap and so a full-surface application of
material from the material film occurs with each laser pulse in the
focus region.
It is particularly advantageous, especially in order to exploit the
material film in an optimum manner, for the focus regions of
successive laser pulses to be positioned on the material film so as
to be adjacent one another.
Within the scope of the explanations concerning the above
embodiments no details have so far been given as to how a
structured layer can be advantageously built up. It is, for
example, particularly advantageous for the focus to be moved
relative to the material film from laser pulse to laser pulse and
for the material film to be moved relative to the process substrate
after a predetermined number of laser pulses. This means that
either the material film can be moved while the process substrate
is stationary or the process substrate can be moved relative to the
material film.
In particular when the material film is very thin, this would mean
that, first of all, at least one partial area of the structured
layer is applied in the form of a thin part layer having the
desired dimension and then a relative movement takes place between
material film and process substrate in order to apply a further
thin part layer thereto.
In this respect, it is particularly advantageous for the material
film to be arranged at a distance from the surface region of the
process substrate which is less than ten times a diameter of the
focus.
In order, in addition, to obtain an imaging or focusing quality
which is as good as possible, the distance of the material film
from the surface of the process substrate is less than 100 .mu.m.
The material film is preferably arranged at a distance of less than
10 .mu.m from the surface of the process substrate. It is even more
advantageous for the distance to be even less and, for example, in
an extreme case for the material film to rest essentially on the
surface of the process substrate.
Especially when using a transparent carrier as carrier for the
material film, it has proven advantageous for an optical focusing
means for the laser beam to be arranged on a side of the
transparent carrier remote from the material film.
It is particularly favourable for the optical focusing means to be
coupled to the transparent carrier by means of an immersion fluid
so that the possibility is given of focusing onto a focus, the
dimension of which can be smaller than the wavelength of the laser
beam. This embodiment offers, in particular, the advantage of
producing very fine and precisely structured layers.
Alternatively to providing a transparent plate, to which the
optical focusing means is coupled by means of an immersion fluid,
it is advantageous for the optical focusing means to be arranged on
the carrier in optical contact and in a reflection-free manner,
i.e. the optical focusing means and the carrier form a unit so that
the immersion fluid can be omitted.
This is possible, in particular, when the optical focusing means is
integrally connected to the carrier.
With such a design of optical focusing means and carrier the
inventive process can preferably be carried out in that prior to an
application of material from the material film to the process
substrate the material film itself is applied to the carrier by
means of the laser used for the application of the structured
layer. The great advantage of this solution is therefore to be seen
in the fact that the laser beam used for the application of the
structured layer can be used at the same time to apply the material
film itself to the carrier whereas the embodiments of the inventive
solution described so far did not specify how the material film is
to be applied to the carrier. In the embodiments described thus
far, this is conceivable by way of a customary vapor-deposition
process or even a laser coating process.
In the embodiment described in the above, it is particularly
advantageous for the laser beam to irradiate the carrier for
applying the material thereto, i.e. the arrangement of carrier and
laser beam relative to one another which is used is the same as for
the application of the structured layer to the process
substrate.
In this respect, the carrier is preferably arranged at a distance
from a surface of a material target for the application of the
material film so that when the carrier is irradiated by the laser
beam the laser beam strikes the surface of the material target.
The distance is preferably selected such that it is more than 1 mm,
in particular a few millimeters.
With a particularly advantageous coating of the carrier, the
material of the material target is heated on its surface by the
laser beam, expands in the direction of the carrier and is
deposited on the carrier in a deposition region. With this
inventive solution, it is, therefore, not the entire carrier which
is provided with the material film but only the deposition
region.
Such a coating of the carrier may be achieved particularly
advantageously when the laser beam is focused onto a surface of the
material target during the application of the material film.
With this inventive solution, and following the coating of the
carrier with the material film, the structured layer is applied in
the same manner as in the aforementioned process with carrier, i.e.
the laser beam is again focused after the material film is applied
to the carrier such that one focus thereof is preferably located
approximately in the plane of the material film or on the surface
of the material film facing the laser beam.
Since, in the embodiments of the inventive process described in the
above, carrier and optical focusing means form one unit, relative
movement of the carrier for the purpose of focusing is no longer
possible. In order, nevertheless, to be able to use the entire
material of the material film in the deposition region for the
application of the structured layer, it is advantageous for the
focus of the laser beam to be moved relative to the carrier for the
structured application of the material from the material film to
the substrate.
This may be achieved particularly advantageously when the focus is
moved by movement of the laser beam relative to the carrier and to
the optical focusing means, whereby the carrier and the optical
focusing means, in particular, form a mutually displaceable
unit.
With respect to the composition of the material film, no precise
details have so far been given. It is, for example, particularly
favourable for the material film to have a material composition
functionally ready for the structured layer of the functional
structure. This means that following the application of the
structured layer with the material film the functionally ready
layer is on hand and, for example, no subsequent doping thereof
need take place.
So far, no details have been given with respect to the ambient
conditions for performing the inventive process. In a particularly
advantageous embodiment of the inventive process, the application
of the structured layer is performed under high vacuum or
ultra-high vacuum since, in this way in particular, the required
quality of the semiconductor components can be achieved in a simple
manner and, moreover, the great advantages of the inventive
solution as regards soiling take full effect.
Furthermore, the invention relates to an apparatus for applying
structured layers of a functional structure of a semiconductor
component which is characterized in that this comprises a material
film which can be positioned above a surface region of a process
substrate to be provided with the structured layer, that the
material film is acted upon on its side remote from the process
substrate by a focus of a laser beam of a laser located in a
defined position corresponding to the structured layer to be
produced and that the material in the material film can be heated
with the laser beam in the region of the focus and material from
the material film can thereby be transferred from the focus region
onto the surface region.
The advantage of the inventive solution is, in the same manner as
in the inventive process, to be seen in the fact that a structured
layer can hereby be applied in a simple and defined manner to a
process substrate.
Additional advantageous embodiments of the inventive apparatus are
the subject matter of the additional subclaims 34 to 44 and,
moreover, additional advantageous features of the inventive
apparatus have already been specified in conjunction with the above
explanations of the inventive process. Reference is therefore made
in full to the above comments with respect, in particular, to the
advantages which can be attained with the additional
embodiments.
Additional features and advantages of the invention are the subject
matter of the following description as well as the drawings of
several embodiments of the inventive solution. In the drawings:
FIG. 1 is an illustration of a first embodiment of an inventive
coating station for the application of structured layers;
FIG. 2 is a schematic illustration of a structured layer;
FIG. 3 is an enlarged illustration of a detail, showing relations
in the region of a focus in FIG. 1;
FIG. 4 is an illustration of a second embodiment for the
application of a structured layer;
FIG. 5 is a schematic illustration of the structured layer during
application in accordance with the second embodiment according to
FIG. 4;
FIG. 6 is an enlarged illustration of a detail in the region of the
focus in a first variation of the second embodiment according to
FIG. 4;
FIG. 7 is an illustration similar to FIG. 6 of a second variation
of the second embodiment during production of the material film
and
FIG. 8 is an illustration of the second variation during production
of a structured layer.
In one embodiment of an inventive solution, illustrated in FIG. 1,
a structuring coating of a process substrate 12b in the form of,
for example, individual webs takes place in a coating apparatus 10
for structured layers.
As illustrated in FIG. 1, the process substrate 12b is held with
the applied layers on a substrate carrier 16 which, for its part,
is displaceable on a base unit 18 in an X and a Z direction,
whereby a surface 20 of the functional structure 27 extends
parallel to the XZ plane.
The base unit 18 has, for this purpose, a drive 22, with which the
process substrate 12b, together with its functional structure, can
be positioned exactly in the XZ plane.
A metal foil 24 forming a material film can be placed on the
surface 20 and the material of this foil is intended to be
metallizable onto the surface 20 in a structured manner, i.e., for
example, in strips or in a meandering shape.
The metallization hereby represents one embodiment for the
application of structured layers. In the same way, the embodiments
described can also serve to apply structured semiconductor layers,
whereby the material film then comprises semiconductor material
with the respectively desired composition and doping.
This metal foil 24 preferably has a thickness of less than 5
micrometers.
In addition, this foil 24 is fixed in position, for example, at an
outer edge 26 of a retainer ring 28 and with a free region 30 is
tensioned without support within the outer edge 26 extending all
around it. This free region can be placed onto the surface 20. In
addition, the retainer ring 28 can be moved towards or away from
the surface 20 by an adjusting means 32 so that after positioning
of the process substrate 12b the entire foil 24 can be positioned,
due to movement of the retainer ring 28 by the adjusting means 32
towards the surface 20, at a distance of, for example, a few .mu.m
from the surface 20 or be placed directly on this surface with its
front side 34.
If the foil 24 is positioned with its front side 34 relative to the
surface 20 of the functional structure 27 as illustrated, a strip
36 illustrated in FIG. 2 is, for example, metallized onto the
surface 20 by irradiation of a rear side 38 of the foil 24 by means
of the laser beam 44. In this respect, the laser beam 44 is focused
with a section 44b onto a focus 40 on the rear side 38 of the foil
24. For this purpose, an optical imaging means 42 is provided
which, for its part, is also positionable in an XZ plane by means
of a double carriage system 45. This optical imaging means 42
comprises a deflecting mirror 46 for a section 44a of the laser
beam 44 incoming parallel to the XY plane as well as a lens 48
arranged after the mirror which focuses the section 44b of the
laser beam 44 onto the focus 40. The laser beam 44 is preferably
generated by a schematically illustrated laser 50.
The surface 20 is now metallized in that a plasma is generated in
the focus 40 from the material of the foil 24, the plasma particles
of which move, on the one hand, along the arrows 52 in the
direction towards the optical imaging means 42 (FIG. 3), these
preferably being particles from the material of the foil 24 located
on the rear side 38.
This automatically leads to material or particles located on the
front side 34 of the foil 24 being accelerated in the direction of
arrows 54 by a pressure surge resulting during the plasma
generation, thereby striking the surface 20 of the process
substrate and being fixed in position on this surface.
As a result of movement of the focus 40 relative to the foil 24,
optional strips 36 or even round metallized areas 56 can be
produced on the surface 20, whereby it is also possible to produce
more complicated structures, for example complicated path conductor
structures, on the surface 20.
In a second embodiment of the inventive coating apparatus 10,
illustrated in FIG. 4, the foil 24 is replaced by a transparent
plate 60, to the front side 62 of which, i.e. the side facing the
surface 20, a metal film 64 is applied, i.e., for example,
vapor-deposited, as material film. This film has a thickness in the
order of an absorption depth of the laser radiation in this metal
film 64. This thickness is, in particular, less than 0.1 .mu.m,
preferably 30 nm or less.
The transparent plate 60 is supported by the retainer ring 28 in
the same way and movable by the adjusting means 32 in the same way
as the foil 24 relative to the surface 20. The laser beam 44b is
thereby focused onto a rear side 66 of the metal film 64, i.e. the
side resting on the transparent plate 60, and when striking this
side generates a plasma from the material of the metal film 64 so
that parts of the material of the metal film 64, in particular on a
front side 68 thereof, are accelerated onto the surface 20 in the
direction of the arrow 70, strike this surface and are thereby
fixed in position.
The advantage of this embodiment is to be seen in the fact that
this allows the metal film to be thinner than the foil 24, for
example so thin that the plasma extends through the thickness of
the metal film 64 so that particles from the plasma are deposited
on the surface 20 and form a part layer which is in the range of a
few nm so that several part layers are to be placed on top of one
another to build up a greater layer thickness.
Furthermore, especially for the application of thicker
metallizations, several metallizing layers are applied on top of
one another, i.e., for example, a first part layer is applied, then
the transparent plate 60 with the metal film 64 displaced to such
an extent that a second and, where necessary, a third part layer
can be applied.
In order to utilize the entire surface of the foil 24 or the metal
film 64 for the metallization, the laser beam 44b is displaceable
due to displacement of the optical imaging means 42 essentially
over the entire inner region of the retainer ring 28. Furthermore,
the process substrate 12b with the functional structure 27 is also
displaceable so that successive increasing areas of the foil 24 or
of the metal film 64 can be used for metallizing the surface 20.
This leads to a utilization of the free region 30 of the foil 24 or
the metal film 64 which is as effective as possible.
For this purpose, a control 72 is provided which controls both the
movement of the laser beam 44b and the relative movement of the
substrate 12b with the functional structure 27 and, in particular,
memorizes which areas of the foil 24 or the metal film 64 have
already been ablated by plasma generation and are, therefore, no
longer available for the further structured metallization. This
means that use of the material of the foil 24 or of the metal film
64 is as effective as possible.
As illustrated in FIG. 5, the focus preferably has a diameter D
which is smaller than a width B of a structure to be metallized,
for example of the strip 36, so that the structure to be applied
results from repeated application of the metallization and each
time with the diameter D of the focus 40.
In a variation of the second embodiment, illustrated in FIG. 6, an
additional focusing element 74 is arranged on the transparent plate
60. This additional focusing element comprises a first focusing
lens 76 and a second focusing lens 78, whereby the second focusing
lens rests with a flat underside 80 on a rear side 82 of the
transparent plate 60 remote from the metal film 64 and an immersion
fluid 84 is arranged between the underside 80 and the rear side 82.
The first lens 76 already bundles the laser beam 44b and images
this onto the second lens 78. Due to the fact that the laser beam,
following the second lens, always extends into material having a
refraction index greater than 1, an additional focusing takes place
onto a focus 40' and this can be smaller than the wavelength of the
laser beam. This means that particularly small structures can be
produced.
The focusing element 74 is, for its part, held in a housing 86 and
also moved with the laser beam 44b, i.e. with the carriage system
45, whereby the second lens 78 floats, so-to-speak, on the
immersion fluid 84 when the laser beam 44b moves relative to the
transparent plate 60.
In a second variation of the second embodiment, illustrated in
FIGS. 7 and 8, the focusing element 74 which is used in the first
variation is used again here. In contrast to the first variation,
the second lens 78 of the focusing element is seated directly on
and in optical contact, i.e. reflection-free, with the carrier 60'
which, in this second variation, is preferably merely of a size
which corresponds to a diameter of the underside 80 of the second
lens 78.
In contrast to the first variation, in which the basis is a carrier
60 coated with the metal film 64, whereby no details whatsoever
have been given concerning the application of the metal film 64 to
the carrier 60 and which can therefore take place as required, for
example by conventional vapor-deposition, in the second variation
as illustrated in FIG. 7 the metal film 64 is applied to the
carrier by means of the laser beam used for the application of the
structured layer.
For this purpose, the laser beam 44b, as illustrated in FIG. 7, is
expanded by insertion of an expansion lens 88 in such a manner that
it is essentially focused onto an irradiation spot 94 of a material
target 90 when the carrier 60' is positioned with its front side
62' at a distance of a few millimeters from a surface 92 of the
material target.
In the irradiation spot 94 the material of the material target is
therefore heated, preferably to form a plasma, which expands in the
form of a cone 96 in the direction of the carrier 60' and is
deposited as metal film 64' on the front side 62', namely in a
deposition region 98 determined by a cross section of the cone
96.
Following the coating of the front side 62' of the carrier 60' in
the deposition region 98, the carrier 60', as illustrated in FIG.
8, is moved over the process substrate 12b and positioned in the
manner already described above at a distance from the surface of
the process substrate 12b.
Furthermore, the expansion lens 88 is withdrawn so that the laser
beam 44b--as already described in conjunction with the first
variation--is now fixed onto the focus 40' which lies approximately
in the plane of the material film 64'.
This means that it is possible to apply a structured layer to the
surface 20 of the process substrate by means of the laser beam 44b
focused in the same manner as in the first variation by generating
a plasma. This application has already been described in detail in
conjunction with the second embodiment and its first variation and
so reference is made in full to the subject matter thereof.
Furthermore, in order to remove the metal film 64' in the entire
deposition region 98, the focus 40' is moved within the deposition
region 98 due to displacement of the laser beam 44b relative to the
carrier 60' and the entire focusing element 74. Thus, the entire
deposition region 98 can be utilized for the application of parts
of a structured layer on the surface 20 of the process substrate
12b and the metal film 64' is not applied again in the manner
described in conjunction with FIG. 7 until the entire deposition
region 98 has been removed.
This means that with the single application of a metal film 64' in
the deposition region 98 a multiple structured application of
layers to the surface 20 of the process substrate 12b is possible
before a renewed application of the metal film 64' in the
deposition area 98 must take place.
As laser, a laser having a pulse duration of 1 to 100 picoseconds
can also be used, whereby the wavelength is between approximately
0.2 and 1.2 .mu.m and the light density is greater than 10.sup.8
w/cm.sup.2, preferably around 10.sup.9 but no more than 10.sup.10
w/cm.sup.2 in the region of the focus 40 in the second embodiment
and in the first embodiment preferably more than 10.sup.10
w/cm.sup.2.
The metallization is preferably carried out in all the embodiments
in a high vacuum so that the entire arrangement described in the
above is arranged in a housing 75 which is accessible via lock
means.
In this case, measures must be taken in the first embodiment to
prevent any soiling of the optical imaging means 42 by the foil 24.
For example, the optical imaging means 42 is provided with a
particle intercepting shield 58 extending around the laser beam
44b. An electrical field 59 is formed between this shield and the
foil 24 and the particles move along this electrical field when a
plasma is generated so that any soiling, in particular, of the lens
48 is avoided.
Alternatively, it is conceivable to provide a flow of protective
gas penetrating the laser beam 44b.
These measures are superfluous in the second embodiment described
in FIG. 4 since a protection of the optical imaging means 42 is
already ensured by the transparent plate.
A suitable laser system is, for example, a conventional system
generating picosecond pulses with the specified power. A laser
system, which is known from German patent 40 22 817, is preferably
used.
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